FREMONT — A Fremont man suspected of killing his mother last week told detectives he hit the retired teacher over the head with an ax, shot her in the back at least four times, then sliced her chest open with a knife, according to court documents released Tuesday.

Omar Malik Pettigen was arrested Sunday and has been charged with murder and desecration of human remains in the death of his mother, 64-year-old Nailah Pettigen, a retired special education teacher at American High School.

The 31-year-old was arraigned Tuesday afternoon in a Fremont courtroom, where he was hidden from public view. More than a dozen of his friends sat in the courtroom gallery in support of Pettigen. He only spoke to confirm his name and will be represented by the county’s public defender office.

In statements to detectives, Omar Pettigen described a brutal killing and disemboweling of his mother on Sept. 28. He said his mother, who he claimed was addicted to oxycodone from hip and knee problems, pointed a gun at him while sitting on her bed, according to court documents.

Pettigen described brutally assaulting his mother with a tomahawk ax and shooting her several times, according to a court affidavit by Fremont police Detective Craig Gaches. It was not known whether Omar Pettigen used the same gun he said his mother pointed at him.

An Alameda County Coroner’s Office autopsy determined she was shot through the head once, had six bullet wounds in her back, and had been cut open from her chin to her cervix.

Pettigen then showered and rested before heading to San Francisco to rent a hotel room. He stopped by a friend’s work to say hello and invited the friend to have beers later, according to Gaches.

Fremont police found Nailah Pettigen dead at 11:02 a.m. Sept. 29 inside her apartment at 3939 Monroe Ave. Officers were conducting a welfare check requested by her ex-husband and the suspect’s father who said the mother and son were not answering their phones. The family had scheduled to pray together over the phone, his father told police.

According to the father, Nailah Pettigen had not been getting along with her son recently and the family had noticed a change in him since he returned from Morocco about a month ago. Omar Pettigen had been living in a tent and working on a marijuana farm north of Sacramento.

Pettigen was arrested Sunday by Kensington police. In addition to his statements to investigators, surveillance footage and cell phone evidence place him at his mother’s apartment around the time of the killing, according to police. His DNA, clothing and footprints were collected by police.

Pettigen, who has been booked at Santa Rita Jail, will return to court Wednesday morning.

“I asked how he felt about his actions and he said good,” Gaches wrote. “During the interview, Omar did not show any signs of remorse by crying or being upset in any way.”